1.Field of the Invention
The present invention relates to the general field of roll shades for windows and, more specifically, to roll shade installations in which a seal is formed between each side margin of the shade and the adjacent upright side of the window frame.
2. Prior Art
A conventional roll shade consisting of flexible sheet material wound on a roller typically is installed at the inside of a window so that the sheet material can be unwound from the roller to obstruct light passing through the window. When formed of air-impervious material, the shade also has an insulating effect by blocking the free flow of air from the inside surface of the window. The insulating effect can be increased by sealing the side margins of the shade to the opposite upright sides of the window frame.
There have been prior attempts to form such a seal without undue interference with smooth operation of the shade. U.S. Pat. No. 2,247,634, issued Jul. 1, 1941, to Houston, for example, discloses a complicated construction including metal channels or tracks secured to the opposite upright sides of the window frame to receive the side margins of the shade (the "secondary window" in the terminology of the Houston patent). The metal channels receive "preshaped strips" of resilient material which are "snapped into place" in the channels and "remain there under tension" such that the strips "press lightly against the edge portion of the secondary window when it is between the strips" (see the paragraph beginning at the right column of page 2, line 21, of the patent).
Other constructions in which the side margins of a roll shade are captured in tracks at the sides of the window frame or a seal of the side edges of the shade to the window frame is otherwise attempted are disclosed in the following U.S. patents:
No. 2,871,933, issued Feb. 3, 1959 (Kroger); PA1 No. 4,357,978, issued Nov. 9, 1982 (Keller et al.); PA1 No 4,369,827, issued Jan. 25, 1983 (Anderson); PA1 No. 4,398,585, issued Aug. 16, 1983 (Marlow); PA1 No. 4,399,855, issued Aug. 23, 1983 (Volfson); PA1 No. 4,408,650, issued Oct. 11, 1983 (Verch); PA1 No. 4,499,937, issued Feb. 19, 1985 (Waine et al.).; PA1 No. 4,649,981, issued Mar. 17, 1987 (Bibeau).
Some of the devices disclosed in the above patents are hard to install, or interfere unduly with retraction of the shade, or are of complicated construction and therefore expensive.